A PLC (programmable logic controller) is a electronic device used for industrial control systems. The basic units have a CPU (a computer processor) that is dedicated to run one program that monitors a series of different inputs and logically manipulates the outputs for the desired control.
They are meant to be very flexible in how they can be programmed while also providing the advantages of high reliability (no program crashes or mechanical failures), compact and economical over traditional control systems.
PLCs are constructed from central processors complemented by memory that is backed up by battery or non-volatile memory. The systems take numerous inputs and output many functions, while monitoring conditions and providing feedback. The CPU of a PLC continually loops through input scan, program scan, output scan and housekeeping modes.
The PLC can be used in different fields as oil refineries, manufacturing lines, conveyor systems and so on.
PLC.
Bibliography
www.plcdev.com
http://www.abcinnova.com/articulos-e-informacion/18-ique-es-un-plc-y-que-beneficios-tiene.html
http://whatis.techtarget.com/definition/programmed-logic-controller-PLC